drivers/net/xen-netback/netback.c:886:7: warning: variable 'pending_idx' set but not used

From: kernel test robot
Date: Sun Feb 19 2023 - 18:57:00 EST

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Hi Ross,

FYI, the error/warning still remains.

tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: c9c3395d5e3dcc6daee66c6908354d47bf98cb0c
commit: ad7f402ae4f466647c3a669b8a6f3e5d4271c84a xen/netback: Ensure protocol headers don't fall in the non-linear area
date: 3 months ago
config: x86_64-randconfig-a015-20230220 (https://download.01.org/0day-ci/archive/20230220/202302200719.wP3xBxCC-lkp@xxxxxxxxx/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad7f402ae4f466647c3a669b8a6f3e5d4271c84a
git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git fetch --no-tags linus master
git checkout ad7f402ae4f466647c3a669b8a6f3e5d4271c84a
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 olddefconfig
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/net/xen-netback/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Link: https://lore.kernel.org/oe-kbuild-all/202302200719.wP3xBxCC-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

>> drivers/net/xen-netback/netback.c:886:7: warning: variable 'pending_idx' set but not used [-Wunused-but-set-variable]
u16 pending_idx;
^
1 warning generated.

vim +/pending_idx +886 drivers/net/xen-netback/netback.c

210c34dcd8d912 Paul Durrant 2015-09-02 871
e9ce7cb6b10740 Wei Liu 2014-06-04 872 static void xenvif_tx_build_gops(struct xenvif_queue *queue,
bdab82759b8e36 Zoltan Kiss 2014-04-02 873 int budget,
bdab82759b8e36 Zoltan Kiss 2014-04-02 874 unsigned *copy_ops,
bdab82759b8e36 Zoltan Kiss 2014-04-02 875 unsigned *map_ops)
f942dc2552b8bf Ian Campbell 2011-03-15 876 {
2475b22526d702 Ross Lagerwall 2015-08-03 877 struct sk_buff *skb, *nskb;
f942dc2552b8bf Ian Campbell 2011-03-15 878 int ret;
2475b22526d702 Ross Lagerwall 2015-08-03 879 unsigned int frag_overflow;
f942dc2552b8bf Ian Campbell 2011-03-15 880
e9ce7cb6b10740 Wei Liu 2014-06-04 881 while (skb_queue_len(&queue->tx_queue) < budget) {
f942dc2552b8bf Ian Campbell 2011-03-15 882 struct xen_netif_tx_request txreq;
376414945d15aa Wei Liu 2013-05-02 883 struct xen_netif_tx_request txfrags[XEN_NETBK_LEGACY_SLOTS_MAX];
f942dc2552b8bf Ian Campbell 2011-03-15 884 struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX-1];
562abd39a19027 Paul Durrant 2016-03-10 885 unsigned int extra_count;
f942dc2552b8bf Ian Campbell 2011-03-15 @886 u16 pending_idx;
f942dc2552b8bf Ian Campbell 2011-03-15 887 RING_IDX idx;
f942dc2552b8bf Ian Campbell 2011-03-15 888 int work_to_do;
f942dc2552b8bf Ian Campbell 2011-03-15 889 unsigned int data_len;
f942dc2552b8bf Ian Campbell 2011-03-15 890 pending_ring_idx_t index;
f942dc2552b8bf Ian Campbell 2011-03-15 891
e9ce7cb6b10740 Wei Liu 2014-06-04 892 if (queue->tx.sring->req_prod - queue->tx.req_cons >
48856286b64e4b Ian Campbell 2013-02-06 893 XEN_NETIF_TX_RING_SIZE) {
e9ce7cb6b10740 Wei Liu 2014-06-04 894 netdev_err(queue->vif->dev,
48856286b64e4b Ian Campbell 2013-02-06 895 "Impossible number of requests. "
48856286b64e4b Ian Campbell 2013-02-06 896 "req_prod %d, req_cons %d, size %ld\n",
e9ce7cb6b10740 Wei Liu 2014-06-04 897 queue->tx.sring->req_prod, queue->tx.req_cons,
48856286b64e4b Ian Campbell 2013-02-06 898 XEN_NETIF_TX_RING_SIZE);
e9ce7cb6b10740 Wei Liu 2014-06-04 899 xenvif_fatal_tx_err(queue->vif);
e9d8b2c2968499 Wei Liu 2014-04-01 900 break;
48856286b64e4b Ian Campbell 2013-02-06 901 }
48856286b64e4b Ian Campbell 2013-02-06 902
09e545f7381459 Juergen Gross 2022-05-30 903 work_to_do = XEN_RING_NR_UNCONSUMED_REQUESTS(&queue->tx);
b3f980bd827e6e Wei Liu 2013-08-26 904 if (!work_to_do)
b3f980bd827e6e Wei Liu 2013-08-26 905 break;
f942dc2552b8bf Ian Campbell 2011-03-15 906
e9ce7cb6b10740 Wei Liu 2014-06-04 907 idx = queue->tx.req_cons;
f942dc2552b8bf Ian Campbell 2011-03-15 908 rmb(); /* Ensure that we see the request before we copy it. */
68a33bfd8403e4 David Vrabel 2015-10-30 909 RING_COPY_REQUEST(&queue->tx, idx, &txreq);
f942dc2552b8bf Ian Campbell 2011-03-15 910
f942dc2552b8bf Ian Campbell 2011-03-15 911 /* Credit-based scheduling. */
e9ce7cb6b10740 Wei Liu 2014-06-04 912 if (txreq.size > queue->remaining_credit &&
e9ce7cb6b10740 Wei Liu 2014-06-04 913 tx_credit_exceeded(queue, txreq.size))
b3f980bd827e6e Wei Liu 2013-08-26 914 break;
f942dc2552b8bf Ian Campbell 2011-03-15 915
e9ce7cb6b10740 Wei Liu 2014-06-04 916 queue->remaining_credit -= txreq.size;
f942dc2552b8bf Ian Campbell 2011-03-15 917
f942dc2552b8bf Ian Campbell 2011-03-15 918 work_to_do--;
e9ce7cb6b10740 Wei Liu 2014-06-04 919 queue->tx.req_cons = ++idx;
f942dc2552b8bf Ian Campbell 2011-03-15 920
f942dc2552b8bf Ian Campbell 2011-03-15 921 memset(extras, 0, sizeof(extras));
562abd39a19027 Paul Durrant 2016-03-10 922 extra_count = 0;
f942dc2552b8bf Ian Campbell 2011-03-15 923 if (txreq.flags & XEN_NETTXF_extra_info) {
e9ce7cb6b10740 Wei Liu 2014-06-04 924 work_to_do = xenvif_get_extras(queue, extras,
562abd39a19027 Paul Durrant 2016-03-10 925 &extra_count,
f942dc2552b8bf Ian Campbell 2011-03-15 926 work_to_do);
e9ce7cb6b10740 Wei Liu 2014-06-04 927 idx = queue->tx.req_cons;
48856286b64e4b Ian Campbell 2013-02-06 928 if (unlikely(work_to_do < 0))
b3f980bd827e6e Wei Liu 2013-08-26 929 break;
f942dc2552b8bf Ian Campbell 2011-03-15 930 }
f942dc2552b8bf Ian Campbell 2011-03-15 931
210c34dcd8d912 Paul Durrant 2015-09-02 932 if (extras[XEN_NETIF_EXTRA_TYPE_MCAST_ADD - 1].type) {
210c34dcd8d912 Paul Durrant 2015-09-02 933 struct xen_netif_extra_info *extra;
210c34dcd8d912 Paul Durrant 2015-09-02 934
210c34dcd8d912 Paul Durrant 2015-09-02 935 extra = &extras[XEN_NETIF_EXTRA_TYPE_MCAST_ADD - 1];
210c34dcd8d912 Paul Durrant 2015-09-02 936 ret = xenvif_mcast_add(queue->vif, extra->u.mcast.addr);
210c34dcd8d912 Paul Durrant 2015-09-02 937
562abd39a19027 Paul Durrant 2016-03-10 938 make_tx_response(queue, &txreq, extra_count,
210c34dcd8d912 Paul Durrant 2015-09-02 939 (ret == 0) ?
210c34dcd8d912 Paul Durrant 2015-09-02 940 XEN_NETIF_RSP_OKAY :
210c34dcd8d912 Paul Durrant 2015-09-02 941 XEN_NETIF_RSP_ERROR);
210c34dcd8d912 Paul Durrant 2015-09-02 942 push_tx_responses(queue);
210c34dcd8d912 Paul Durrant 2015-09-02 943 continue;
210c34dcd8d912 Paul Durrant 2015-09-02 944 }
210c34dcd8d912 Paul Durrant 2015-09-02 945
210c34dcd8d912 Paul Durrant 2015-09-02 946 if (extras[XEN_NETIF_EXTRA_TYPE_MCAST_DEL - 1].type) {
210c34dcd8d912 Paul Durrant 2015-09-02 947 struct xen_netif_extra_info *extra;
210c34dcd8d912 Paul Durrant 2015-09-02 948
210c34dcd8d912 Paul Durrant 2015-09-02 949 extra = &extras[XEN_NETIF_EXTRA_TYPE_MCAST_DEL - 1];
210c34dcd8d912 Paul Durrant 2015-09-02 950 xenvif_mcast_del(queue->vif, extra->u.mcast.addr);
210c34dcd8d912 Paul Durrant 2015-09-02 951
562abd39a19027 Paul Durrant 2016-03-10 952 make_tx_response(queue, &txreq, extra_count,
562abd39a19027 Paul Durrant 2016-03-10 953 XEN_NETIF_RSP_OKAY);
210c34dcd8d912 Paul Durrant 2015-09-02 954 push_tx_responses(queue);
210c34dcd8d912 Paul Durrant 2015-09-02 955 continue;
210c34dcd8d912 Paul Durrant 2015-09-02 956 }
210c34dcd8d912 Paul Durrant 2015-09-02 957
ad7f402ae4f466 Ross Lagerwall 2022-11-22 958 data_len = (txreq.size > XEN_NETBACK_TX_COPY_LEN) ?
ad7f402ae4f466 Ross Lagerwall 2022-11-22 959 XEN_NETBACK_TX_COPY_LEN : txreq.size;
ad7f402ae4f466 Ross Lagerwall 2022-11-22 960
562abd39a19027 Paul Durrant 2016-03-10 961 ret = xenvif_count_requests(queue, &txreq, extra_count,
562abd39a19027 Paul Durrant 2016-03-10 962 txfrags, work_to_do);
ad7f402ae4f466 Ross Lagerwall 2022-11-22 963
48856286b64e4b Ian Campbell 2013-02-06 964 if (unlikely(ret < 0))
b3f980bd827e6e Wei Liu 2013-08-26 965 break;
48856286b64e4b Ian Campbell 2013-02-06 966
f942dc2552b8bf Ian Campbell 2011-03-15 967 idx += ret;
f942dc2552b8bf Ian Campbell 2011-03-15 968
f942dc2552b8bf Ian Campbell 2011-03-15 969 if (unlikely(txreq.size < ETH_HLEN)) {
e9ce7cb6b10740 Wei Liu 2014-06-04 970 netdev_dbg(queue->vif->dev,
f942dc2552b8bf Ian Campbell 2011-03-15 971 "Bad packet size: %d\n", txreq.size);
562abd39a19027 Paul Durrant 2016-03-10 972 xenvif_tx_err(queue, &txreq, extra_count, idx);
b3f980bd827e6e Wei Liu 2013-08-26 973 break;
f942dc2552b8bf Ian Campbell 2011-03-15 974 }
f942dc2552b8bf Ian Campbell 2011-03-15 975
f942dc2552b8bf Ian Campbell 2011-03-15 976 /* No crossing a page as the payload mustn't fragment. */
d0089e8a0e4c97 Julien Grall 2015-05-05 977 if (unlikely((txreq.offset + txreq.size) > XEN_PAGE_SIZE)) {
e9ce7cb6b10740 Wei Liu 2014-06-04 978 netdev_err(queue->vif->dev,
68946159da1b0b Julien Grall 2015-06-16 979 "txreq.offset: %u, size: %u, end: %lu\n",
f942dc2552b8bf Ian Campbell 2011-03-15 980 txreq.offset, txreq.size,
d0089e8a0e4c97 Julien Grall 2015-05-05 981 (unsigned long)(txreq.offset&~XEN_PAGE_MASK) + txreq.size);
e9ce7cb6b10740 Wei Liu 2014-06-04 982 xenvif_fatal_tx_err(queue->vif);
b3f980bd827e6e Wei Liu 2013-08-26 983 break;
f942dc2552b8bf Ian Campbell 2011-03-15 984 }
f942dc2552b8bf Ian Campbell 2011-03-15 985
e9ce7cb6b10740 Wei Liu 2014-06-04 986 index = pending_index(queue->pending_cons);
e9ce7cb6b10740 Wei Liu 2014-06-04 987 pending_idx = queue->pending_ring[index];
f942dc2552b8bf Ian Campbell 2011-03-15 988
ad7f402ae4f466 Ross Lagerwall 2022-11-22 989 if (ret >= XEN_NETBK_LEGACY_SLOTS_MAX - 1 && data_len < txreq.size)
ad7f402ae4f466 Ross Lagerwall 2022-11-22 990 data_len = txreq.size;
f942dc2552b8bf Ian Campbell 2011-03-15 991
e3377f36ca20a0 Zoltan Kiss 2014-03-06 992 skb = xenvif_alloc_skb(data_len);
f942dc2552b8bf Ian Campbell 2011-03-15 993 if (unlikely(skb == NULL)) {
e9ce7cb6b10740 Wei Liu 2014-06-04 994 netdev_dbg(queue->vif->dev,
f942dc2552b8bf Ian Campbell 2011-03-15 995 "Can't allocate a skb in start_xmit.\n");
562abd39a19027 Paul Durrant 2016-03-10 996 xenvif_tx_err(queue, &txreq, extra_count, idx);
f942dc2552b8bf Ian Campbell 2011-03-15 997 break;
f942dc2552b8bf Ian Campbell 2011-03-15 998 }
f942dc2552b8bf Ian Campbell 2011-03-15 999
2475b22526d702 Ross Lagerwall 2015-08-03 1000 skb_shinfo(skb)->nr_frags = ret;
2475b22526d702 Ross Lagerwall 2015-08-03 1001 /* At this point shinfo->nr_frags is in fact the number of
2475b22526d702 Ross Lagerwall 2015-08-03 1002 * slots, which can be as large as XEN_NETBK_LEGACY_SLOTS_MAX.
2475b22526d702 Ross Lagerwall 2015-08-03 1003 */
2475b22526d702 Ross Lagerwall 2015-08-03 1004 frag_overflow = 0;
2475b22526d702 Ross Lagerwall 2015-08-03 1005 nskb = NULL;
2475b22526d702 Ross Lagerwall 2015-08-03 1006 if (skb_shinfo(skb)->nr_frags > MAX_SKB_FRAGS) {
2475b22526d702 Ross Lagerwall 2015-08-03 1007 frag_overflow = skb_shinfo(skb)->nr_frags - MAX_SKB_FRAGS;
2475b22526d702 Ross Lagerwall 2015-08-03 1008 BUG_ON(frag_overflow > MAX_SKB_FRAGS);
2475b22526d702 Ross Lagerwall 2015-08-03 1009 skb_shinfo(skb)->nr_frags = MAX_SKB_FRAGS;
2475b22526d702 Ross Lagerwall 2015-08-03 1010 nskb = xenvif_alloc_skb(0);
2475b22526d702 Ross Lagerwall 2015-08-03 1011 if (unlikely(nskb == NULL)) {
3a0233ddec554b Ross Lagerwall 2019-08-05 1012 skb_shinfo(skb)->nr_frags = 0;
2475b22526d702 Ross Lagerwall 2015-08-03 1013 kfree_skb(skb);
562abd39a19027 Paul Durrant 2016-03-10 1014 xenvif_tx_err(queue, &txreq, extra_count, idx);
2475b22526d702 Ross Lagerwall 2015-08-03 1015 if (net_ratelimit())
2475b22526d702 Ross Lagerwall 2015-08-03 1016 netdev_err(queue->vif->dev,
2475b22526d702 Ross Lagerwall 2015-08-03 1017 "Can't allocate the frag_list skb.\n");
2475b22526d702 Ross Lagerwall 2015-08-03 1018 break;
2475b22526d702 Ross Lagerwall 2015-08-03 1019 }
2475b22526d702 Ross Lagerwall 2015-08-03 1020 }
2475b22526d702 Ross Lagerwall 2015-08-03 1021
f942dc2552b8bf Ian Campbell 2011-03-15 1022 if (extras[XEN_NETIF_EXTRA_TYPE_GSO - 1].type) {
f942dc2552b8bf Ian Campbell 2011-03-15 1023 struct xen_netif_extra_info *gso;
f942dc2552b8bf Ian Campbell 2011-03-15 1024 gso = &extras[XEN_NETIF_EXTRA_TYPE_GSO - 1];
f942dc2552b8bf Ian Campbell 2011-03-15 1025
e9ce7cb6b10740 Wei Liu 2014-06-04 1026 if (xenvif_set_skb_gso(queue->vif, skb, gso)) {
7376419a469765 Wei Liu 2013-08-26 1027 /* Failure in xenvif_set_skb_gso is fatal. */
3a0233ddec554b Ross Lagerwall 2019-08-05 1028 skb_shinfo(skb)->nr_frags = 0;
f942dc2552b8bf Ian Campbell 2011-03-15 1029 kfree_skb(skb);
2475b22526d702 Ross Lagerwall 2015-08-03 1030 kfree_skb(nskb);
b3f980bd827e6e Wei Liu 2013-08-26 1031 break;
f942dc2552b8bf Ian Campbell 2011-03-15 1032 }
f942dc2552b8bf Ian Campbell 2011-03-15 1033 }
f942dc2552b8bf Ian Campbell 2011-03-15 1034
c2d09fde7299f6 Paul Durrant 2016-05-13 1035 if (extras[XEN_NETIF_EXTRA_TYPE_HASH - 1].type) {
c2d09fde7299f6 Paul Durrant 2016-05-13 1036 struct xen_netif_extra_info *extra;
c2d09fde7299f6 Paul Durrant 2016-05-13 1037 enum pkt_hash_types type = PKT_HASH_TYPE_NONE;
c2d09fde7299f6 Paul Durrant 2016-05-13 1038
c2d09fde7299f6 Paul Durrant 2016-05-13 1039 extra = &extras[XEN_NETIF_EXTRA_TYPE_HASH - 1];
c2d09fde7299f6 Paul Durrant 2016-05-13 1040
c2d09fde7299f6 Paul Durrant 2016-05-13 1041 switch (extra->u.hash.type) {
c2d09fde7299f6 Paul Durrant 2016-05-13 1042 case _XEN_NETIF_CTRL_HASH_TYPE_IPV4:
c2d09fde7299f6 Paul Durrant 2016-05-13 1043 case _XEN_NETIF_CTRL_HASH_TYPE_IPV6:
c2d09fde7299f6 Paul Durrant 2016-05-13 1044 type = PKT_HASH_TYPE_L3;
c2d09fde7299f6 Paul Durrant 2016-05-13 1045 break;
c2d09fde7299f6 Paul Durrant 2016-05-13 1046
c2d09fde7299f6 Paul Durrant 2016-05-13 1047 case _XEN_NETIF_CTRL_HASH_TYPE_IPV4_TCP:
c2d09fde7299f6 Paul Durrant 2016-05-13 1048 case _XEN_NETIF_CTRL_HASH_TYPE_IPV6_TCP:
c2d09fde7299f6 Paul Durrant 2016-05-13 1049 type = PKT_HASH_TYPE_L4;
c2d09fde7299f6 Paul Durrant 2016-05-13 1050 break;
c2d09fde7299f6 Paul Durrant 2016-05-13 1051
c2d09fde7299f6 Paul Durrant 2016-05-13 1052 default:
c2d09fde7299f6 Paul Durrant 2016-05-13 1053 break;
c2d09fde7299f6 Paul Durrant 2016-05-13 1054 }
c2d09fde7299f6 Paul Durrant 2016-05-13 1055
c2d09fde7299f6 Paul Durrant 2016-05-13 1056 if (type != PKT_HASH_TYPE_NONE)
c2d09fde7299f6 Paul Durrant 2016-05-13 1057 skb_set_hash(skb,
c2d09fde7299f6 Paul Durrant 2016-05-13 1058 *(u32 *)extra->u.hash.value,
c2d09fde7299f6 Paul Durrant 2016-05-13 1059 type);
c2d09fde7299f6 Paul Durrant 2016-05-13 1060 }
c2d09fde7299f6 Paul Durrant 2016-05-13 1061
ad7f402ae4f466 Ross Lagerwall 2022-11-22 1062 xenvif_get_requests(queue, skb, &txreq, txfrags, copy_ops,
ad7f402ae4f466 Ross Lagerwall 2022-11-22 1063 map_ops, frag_overflow, nskb, extra_count,
ad7f402ae4f466 Ross Lagerwall 2022-11-22 1064 data_len);
f942dc2552b8bf Ian Campbell 2011-03-15 1065
e9ce7cb6b10740 Wei Liu 2014-06-04 1066 __skb_queue_tail(&queue->tx_queue, skb);
1e0b6eac6a150a Annie Li 2012-06-27 1067
e9ce7cb6b10740 Wei Liu 2014-06-04 1068 queue->tx.req_cons = idx;
f942dc2552b8bf Ian Campbell 2011-03-15 1069
ad7f402ae4f466 Ross Lagerwall 2022-11-22 1070 if ((*map_ops >= ARRAY_SIZE(queue->tx_map_ops)) ||
e9ce7cb6b10740 Wei Liu 2014-06-04 1071 (*copy_ops >= ARRAY_SIZE(queue->tx_copy_ops)))
f942dc2552b8bf Ian Campbell 2011-03-15 1072 break;
f942dc2552b8bf Ian Campbell 2011-03-15 1073 }
f942dc2552b8bf Ian Campbell 2011-03-15 1074
bdab82759b8e36 Zoltan Kiss 2014-04-02 1075 return;
f942dc2552b8bf Ian Campbell 2011-03-15 1076 }
f942dc2552b8bf Ian Campbell 2011-03-15 1077

:::::: The code at line 886 was first introduced by commit
:::::: f942dc2552b8bfdee607be867b12a8971bb9cd85 xen network backend driver

:::::: TO: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
:::::: CC: David S. Miller <davem@xxxxxxxxxxxxx>

--
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